Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
Patent
1996-05-15
1999-03-09
Alvo, Steven
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Waste paper or textile waste
162 72, 435278, D21H 1120, D21H 2502
Patent
active
058795090
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of PCT/DK94/00437 filed Nov. 23, 1994, which is incorporated herein by reference.
TECHNICAL FIELD
This invention relates to processes for producing a papermaking pulp and producing new paper from old starch-coated printed paper. More particularly, it relates to such processes with improved ink removal leading to improved brightness of the pulp or paper.
BACKGROUND ART
In the recycling of old starch-coated printed paper such as old newspapers and magazines for use in papermaking, it is usually desirable to remove the printing ink in order to produce new paper of high brightness. It is therefore conventional to repulp (or disintegrate) the old paper together with deinking chemicals, such as deinking surfactant, NaOH and sodium silicate, followed by bleaching with hydrogen peroxide and deinking chemicals and by separation of ink particles from the pulp.
A number of documents in the prior art describe the use of enzymes to improve ink removal. Thus, Japanese laid-open patent application Kokai Sho 59-9299 (Kao), Japanese laid-open patent application Kokai Sho 63-59494 (Honshu Paper), Japanese laid-open patent application Kokai Hei 2-80683 (Oji Paper) and WO 91/14819 (Novo Nordisk) describe the use of a cellulase, i.e. an enzyme acting on the cellulose fibers of paper. Japanese laid-open patent application Kokai Hei 2-160984 (Novo Nordisk) and Japanese laid-open patent application Kokai Hei 2-80684 (Lion) describe the use of a lipase, i.e. an enzyme acting on triglycerides in the printing ink.
It is the object of this invention to provide an improved process for removal of printing ink for use in the recycling of old starch-coated paper.
STATEMENT OF THE INVENTION
Surprisingly, we have found that in the production of pulp and paper from starch-coated paper, the deinking effect can be improved by including a treatment with a starch-degrading enzyme.
Accordingly, the invention provides a process for producing a papermaking pulp from starch-coated printed paper, comprising the following steps: and
The invention also provides a process for recycling old starch-coated printed paper into new paper, comprising producing a pulp by the above process, followed by papermaking.
DETAILED DESCRIPTION OF THE INVENTION
The process of the invention is applicable to the recycling of any kind of printed, starch-coated paper. Typical examples are old newspaper, magazines and printed stationery. The paper may contain mineral fillers such as calcium carbonate and clay.
The starch coating may consist of starch from any source and generally contains 20-30% of amylose and the balance amylopectin. Typical examples are corn starch, wheat starch, potato starch, rice starch and tapioca starch. Starch to be used as a coating material will generally be pretreated to achieve a limited hydrolysis by cooking with amylase or acid.
The starch coating may also consist of modified starch. Modified starches useful for paper coating include dextrin (e.g. white dextrin, canary dextrin or British gum), acid-modified starch, oxidized starch (chlorinated starch), hydrozyethylated starch and cationic starch.
The inks to be removed by the process of this invention include but are not limited to non-contact laser inks, xerographic toners, letterpress ink generally used in printing newsprint, magazine print, offset printing ink, ultraviolet or electron beam cured ink.
The disintegration step may be done in a conventional pulper, typically for 5-30 minutes at 3-30% pulp consistency. If the enzyme treatment is completed before the disintegration, conventional deinking chemicals can be used in the disintegration.
Conventional deinking chemicals typically comprise an alkaline reagent and a surfactant. The surfactant can, e.g., be used at a dosage of 0.2-0.6%. The surfactant is preferably nonionic, e.g. ethoxylated octyl or nonyl phenol or any of the nonionic surfactants disclosed in Park et al., 1992, Biotechnology and Bioengineering 39:117-120. The alkaline reagent may be NaO
REFERENCES:
patent: 3616219 (1971-10-01), Massey
patent: 3652383 (1972-03-01), de Vos
patent: 4450043 (1984-05-01), Schulz
Abstract JP -Dialog File 351, WPI Accession No. 84-051743/09.
Sakaguchi Hiromichi
Sharyo Masaki
Shimoto Hidesato
Alvo Steven
Lombinis Elias
Novo Nordisk A S
Zelson Steve T.
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